The present invention relates to methods of inhibiting the corrosion of metal surfaces by aqueous acids and corrosion inhibitor compositions comprising a benzylideneaniline compound and/or a cinnamylideneaniline compound.
Subterranean hydrocarbon containing formations penetrated by well bores are often treated with aqueous acids to stimulate the production of hydrocarbons therefrom. One such treatment, generally referred to as “acidizing,” involves the introduction of an aqueous acid solution into a subterranean formation under pressure so that the acid solution flows through the pore spaces of the formation. The acid reacts with acid soluble materials contained in the formation thereby increasing the size of the pore spaces, thus increasing the permeability of the formation. Another production stimulation treatment known as “fracture-acidizing” involves the formation of one or more fractures in the formation and the introduction of an aqueous acid solution into the fractures to etch the fracture faces whereby channels are formed therein when the fractures close. The acid also enlarges the pore spaces in the fracture faces and in the formation.
Acidizing and fracture-acidizing solutions typically contain, for example, 15% to 28% hydrochloric acid, which can cause corrosion of metal surfaces in pumps, tubular goods and equipment used to introduce the aqueous acid solutions into the subterranean formations to be treated. The expense associated with repairing or replacing corrosion damaged tubular goods and equipment can be problematic. The corrosion of tubular goods and down-hole equipment is increased by the elevated temperatures encountered in deep formations, and the corrosion results in at least the partial neutralization of the acid before it reacts with acid-soluble materials in the formations, which leads to added expense and complications because additional quantities of the acid often are required to achieve the desired result.
Aqueous acid solutions are also utilized in a variety of other industrial applications to contact and react with acid soluble materials. In such applications, metal surfaces are contacted with the acid and any corrosion of the metal surfaces is highly undesirable. In addition, other corrosive fluids such as aqueous alkaline solutions, heavy brines, petroleum streams containing acidic materials and the like are commonly transported through and corrode metal surfaces in tubular goods, pipelines and pumping equipment.
A variety of metal corrosion inhibiting additives has been developed for aqueous acid fluids; however, many of them are considered environmentally objectionable. Cinnamaldehyde, which has favorable environmental characteristics, has been used for years in corrosion inhibitor formulations; however, the cinnamaldehyde molecule by itself provides only limited inhibition in 15% hydrochloric acid at temperatures greater than 225° F. and in 28% hydrochloric acid at temperatures greater than 200° F. Since cinnamaldehyde is one of the more ecologically benign organic materials in acid corrosion inhibitor compositions, improvements in cinnamaldehyde-based chemistry are actively pursued.
Some improvements have been made to the corrosion inhibiting properties of cinnamaldehyde by combining it with aniline, for example. Such compositions, however, can exhibit solubility issues in acidic fluids. Moreover, in some instances, these compositions may not meet current regulatory guidelines for use in certain areas such as the North Sea. Benzaldehyde has been used in some corrosion inhibitor compositions with cinnamaldehyde. Benzaldehyde, although an aldehyde, is not alpha-beta unsaturated, and therefore, does not provide desirable corrosion resistance. This may be due to the electronic effects imparted by the alpha-beta unsaturated moiety, which are believed to be sites for initiation of polymerization at the surface, or for chemisorption to the metal surface.